package thinkinjava4.ch12_exceptions;

class DynamicFieldsException extends Exception {
}

public class DynamicFields {
    private Object[][] fields;

    public DynamicFields(int initialSize) {
        fields = new Object[initialSize][2];
        for (int i = 0; i < initialSize; i++)
            fields[i] = new Object[]{null, null};
    }

    @Override
    public String toString() {
        StringBuilder result = new StringBuilder();
        for (Object[] obj : fields) {
            result.append(obj[0]);
            result.append(": ");
            result.append(obj[1]);
            result.append("\n");
        }
        return result.toString();
    }

    /**
     * 键值是否存在
     *
     * @param id
     * @return -1表示不存在
     */
    private int hasField(String id) {
        for (int i = 0; i < fields.length; i++)
            if (id.equals(fields[i][0]))
                return i;
        return -1;
    }

    /**
     * 获取键值下标
     *
     * @param id
     * @return 键值下标
     * @throws NoSuchFieldException
     */
    private int getFieldNumber(String id) throws NoSuchFieldException {
        int fieldNum = hasField(id);
        if (fieldNum == -1)
            throw new NoSuchFieldException();
        return fieldNum;
    }

    private int makeField(String id) {
        for (int i = 0; i < fields.length; i++)
            if (fields[i][0] == null) {
                fields[i][0] = id;
                return i;
            }
        //如果fields原始空间使用完了，新建一个容量+1的容器，将原数据拷贝到新容器中
        Object[][] tmp = new Object[fields.length + 1][2];
        //将fields中的内容复制到tmp
        System.arraycopy(fields, 0, tmp, 0, fields.length);
        for (int i = fields.length; i < tmp.length; i++) {
            tmp[i] = new Object[]{null, null};
        }
        fields = tmp;
        return makeField(id);
    }

    public Object getField(String id) throws NoSuchFieldException {
        return fields[getFieldNumber(id)][1];
    }

    public Object setField(String id, Object value) throws DynamicFieldsException {
        if (value == null) {
            DynamicFieldsException dfe = new DynamicFieldsException();
            // 原因
            dfe.initCause(new NullPointerException());
            throw dfe;
        }
        int fieldNumber = hasField(id);
        if (fieldNumber == -1)
            fieldNumber = makeField(id);
        Object result;
        try {
            result = getField(id);
        } catch (NoSuchFieldException e) {
            throw new RuntimeException(e);
        }
        fields[fieldNumber][1] = value;
        return result;
    }

    public static void main(String[] args) {
        DynamicFields df = new DynamicFields(3);
        System.out.println(df);
        try {
            df.setField("d", "A value for d");
            df.setField("number", 47);
            df.setField("number2", 48);
            System.out.println(df);

            df.setField("d", "A new value for d");
            System.out.println("df:" + df);
            System.out.println("df.getField(\"d\"):" + df.getField("d"));
            Object field = df.setField("d", null);
        } catch (DynamicFieldsException | NoSuchFieldException e) {
            e.printStackTrace(System.out);
        }
    }
}
